The present application claims priority to Japanese Application No. P10-165108 filed Jun. 12, 1998, which application is incorporated herein by reference to the extent permitted by law.
1. Technical Field
This invention relates generally to a bicycle having a rotating force transmitting mechanism with an oscillating fulcrum point. More particularly, the invention relates to the bicycle wherein a crank lever is arranged between a sprocket and a pedal lever to transmit force applied to the pedal lever to the sprocket, and the oscillating fulcrum point of the pedal lever is slidable.
2. Related Art
The conventional bicycle is operated such that the crank-like pedals fixed at both sides of a shaft of the sprocket with a phase difference of 180xc2x0 are stepped on by a rider. The pedal lever is rotated around the shaft of the sprocket to attain rotating force of the sprocket and this rotating force of the sprocket is transmitted to the rear wheel through the chain.
However, in recent development of the bicycle, there has been proposed to provide a bicycle having a driving force generating device with an oscillating fulcrum point, whereby the rider is less fatigued with a riding as compared with the conventional bicycle, and desired propulsion force can be attained.
FIG. 1 schematically shows a configuration of the related art bicycle having the driving force generating device with an oscillating fulcrum point. In FIG. 1, a bicycle 60 having the rotating force transmitting mechanism with the oscillating fulcrum point is constructed such that respective a front wheel 61 and a rear wheel 62 acting as moving wheel are attached to a pair of delta-shaped frames 63, 64, a handle 65 is attached to a front frame 63 and a saddle 66 is fixed to a rear frame 64. These members are constructed in the same manner as the conventional bicycle.
A wheel shaft 61a of the front wheel 61 is rotatably attached to the extremity ends of a fork section 67a formed at the lower part of a handle frame 67. Connecting portion 63a constituting the front frame 63 is extended longitudinally in a reverse direction which the bicycle is headed, from a holding part 63c holding the handle frame 67 rotatably. Connecting portion 63b also constituting the front frame 63 is extended in a rearward and downwardly slanting direction from the holding part 63c. The extremity ends of these connecting portions 63a, 63b are connected to a saddle frame 64c. The saddle frame 64c constitutes the rear frame 64 and is substantially in parallel with the handle frame 67. The saddle 66 is fixed to this saddle frame 64c. 
Respective connecting portions 64a and 64b constituting the rear frame 64 are extended from the connecting portions 63a and 63b. The extremity ends of these connecting portions 64a, 64b are connected to each other to hold the wheel shaft 62a of the rear wheel 62 horizontally. Respective gears 75R and 75L (not shown) are attached and fixed to both ends of the wheel shaft 62a. FIG. 1 illustrates the configuration of the bicycle in which only the gear 75R at the right side toward a direction which a bicycle is headed, is shown.
The gear 75R is engaged with a gear train, not shown, and the crank 76R is fixed for transmitting its rotating force to the gear 75R through the gear train. A crank pin 77R is fixed to a position displaced in respect to a shaft 78R of the crank 76R. A right side pedal lever 72R holds rotatably the crank pin 77R so that the crank 76R may be rotated with the crank pin 77R.
The right side pedal lever 72R attaches a right side pedal 71R rotatably at a front end thereof. The pedal lever 72R attaches a roller 73R pivotally at a rear end thereof. The roller 73R is freely slid in a guiding groove 74R formed near the wheel shaft 62a. 
The pedal lever 72R acts as a lever oscillating up and down with the roller 73R pivoted at the pedal lever 72R being applied as a fulcrum point.
When the rider steps on the pedal 71R acting as a force applying point, the pedal 71R is moved in a counter-clockwise direction along a locus S approximating to a flat ellipse shape. At the same time, the pedal lever 72R is moved up and down in a predetermined angle with the roller 73R being applied as a fulcrum point.
This motion allows the crank 76R to rotate in a counter-clockwise direction around the shaft 78R through the crank pin 77R acting as a lever force applying point of the pedal lever 72a. At this time, the roller 73R acting as a fulcrum point for the pedal lever 72R is slid (moved) laterally within the guiding groove 74R. That is, the roller 73R acts as an oscillating fulcrum point for the pedal lever 72R.
While the crank 76R is rotated, the rotating force of the crank 76R is transmitted to the gear 75R through the gear train. A clockwise directional rotation of the gear 75R causes the wheel shaft 62a of the rear wheel 62 to rotate for obtaining propulsion force of the bicycle 60. The propulsion force enables the bicycle 60 to run.
Since a left-side pedal lever 72L (not shown) is provided with the same driving force transmitting mechanism as that of the right side pedal lever 72R described above, a rider steps on the pedals 71R and 71L (not shown) alternatively by his (her) right and left feet to obtain propulsion force for the bicycle 60. Thereby, the bicycle 60 may run.
The configuration of the aforesaid bicycle 60, however, requires that the rotating force transmitting mechanisms for use in rotating the rear wheel 62 such as the crank 76R, the gear 75R and the guiding groove 74R constituting the driving force inputting device with an oscillating fulcrum point, are arranged specially at both sides of the frames 63, 64. Due to this fact, such the bicycle has a problem that the number of component parts constituting the bicycle has been increased so that the manufacture of the bicycle has cost up and the body weight of the bicycle 60 is increased.
The object of the present invention is to provide a less-expensive and light weight bicycle in which the configuration of the rotating force transmitting mechanism is made simple and the number of component parts is reduced, and further a smooth locus Q of motion of the pedal can be assured and at the same time rotating force of the sprocket is transmitted efficiently when an oscillating range of the pedal lever is reduced.
In carrying out the invention in one preferred mode, we provide a bicycle comprising a frame constituting a chassis, a pair of moving wheels rotatably arranged at a front side and a rear side of the frame, a sprocket arranged near a bottom bracket point in the frame, driving force transmitting means for transmitting rotating force of the sprocket to the rear wheel, a pair of pedal levers having a phase difference of 180xc2x0 with respect to each other to oscillate alternatively up and down, a crank lever arranged between the sprocket and the one pedal lever so as to transmit force of the pedal lever to the sprocket, and a sliding part for acting as an oscillating fulcrum point of the pedal lever.
A sliding pin arranged at one end of the pedal lever is slid within the sliding part while the pedal lever is oscillated. The force accompanied by the oscillation of the pedal lever is transmitted to the rear wheel through the sprocket.
In the present invention, force applied to the pedal by the rider is transmitted to the rear wheel under utilization of the crank lever, the sprocket and the chain. Namely, the force of the pedal lever is transmitted to the sprocket through the crank lever. The oscillating fulcrum point of the pedal lever is moved, not fixed, laterally in the sliding part.
With such an arrangement, the configuration of the driving force transmitting mechanism for the rear wheel is simplified. This causes the bicycle according to the invention to be light in its weight, and then rotating force of the sprocket is transmitted efficiently when an oscillating range of the pedal lever is reduced.
Then, as the pedal lever is stepped on by the rider, the oscillating fulcrum point is moved laterally, so that when the locus of motion of the pedal is different in reference to the first half period (from the upper dead center to the lower dead center) and the second half period (from the lower dead center to the upper lower center), a smooth motion of the pedal is obtained.
A further understanding of the nature and advantages of the invention may be realized by reference to the following portion of the specification and drawings.